行为变更：所有应用

Android 14 平台包含一些行为变更，这些变更可能会影响您的应用。以下行为变更将影响在 Android 14 上运行的所有应用，无论采用哪种 targetSdkVersion 都不例外。您应该测试您的应用，然后根据需要进行修改，以适当地支持这些变更。

此外，请务必查看仅影响以 Android 14 为目标平台的应用的行为变更列表。

核心功能

默认拒绝设定精确的闹钟

精确的闹钟适用于用户指定的通知，或是在确切时间需要执行的操作。从 Android 14 开始，系统不再向以 Android 13 及更高版本为目标平台的大多数新安装应用预先授予 SCHEDULE_EXACT_ALARM 权限，该权限默认处于拒绝状态。

详细了解安排精确闹钟的权限变化。

当应用进入缓存时，上下文注册的广播将加入队列

在 Android 14 中，当应用处于缓存状态时，系统可以将上下文注册的广播放入队列中。这与 Android 12（API 级别 31）为异步 binder 事务引入的队列行为类似。在清单中声明的广播不会加入队列，并且应用会从缓存状态中移除以进行广播传递。

当应用离开缓存状态（例如返回前台）时，系统会传递所有已加入队列的广播。某些广播的多个实例可以合并为一个广播。根据其他因素（例如系统运行状况），系统可能会从缓存状态中移除应用，并且传输之前加入队列的所有广播。

应用只能终止自己的后台进程

从 Android 14 开始，当您的应用调用 killBackgroundProcesses() 时，该 API 只能终止您自己应用的后台进程。

如果您传入另一个应用的软件包名称，此方法对该应用的后台进程没有影响，并且 Logcat 中会显示以下消息：

Invalid packageName: com.example.anotherapp

您的应用不应使用 killBackgroundProcesses() API，也不得以其他方式尝试影响其他应用的进程生命周期，即使在旧版操作系统上也是如此。Android 旨在让缓存应用在后台运行，并在系统需要内存时自动终止它们。如果您的应用会不必要地终止其他应用，则由于之后需要完全重启这些应用，因此可能会降低系统性能并增加耗电量，这比恢复现有缓存应用所消耗的资源要多得多。

第一个请求 MTU 的 GATT 客户端的 MTU 设置为 517

Starting from Android 14, the Android Bluetooth stack more strictly adheres to Version 5.2 of the Bluetooth Core Specification and requests the BLE ATT MTU to 517 bytes when the first GATT client requests an MTU using the BluetoothGatt#requestMtu(int) API, and disregards all subsequent MTU requests on that ACL connection.

To address this change and make your app more robust, consider the following options:

  • Your peripheral device should respond to the Android device's MTU request with a reasonable value that can be accommodated by the peripheral. The final negotiated value will be a minimum of the Android requested value and the remote provided value (for example, min(517, remoteMtu))
    • Implementing this fix could require a firmware update for peripheral
  • Alternatively, limit your GATT characteristic writes based on the minimum between the known supported value of your peripheral and the received MTU change
    • A reminder that you should reduce 5 bytes from the supported size for the headers
    • For example: arrayMaxLength = min(SUPPORTED_MTU, GATT_MAX_ATTR_LEN(517)) - 5

可将应用放入“受限待机”分桶的新原因

Android 14 introduces a new reason an app can be placed into the restricted standby bucket. The app's jobs trigger ANR errors multiple times due to onStartJob, onStopJob, or onBind method timeouts. (See JobScheduler reinforces callback and network behavior for changes to onStartJob and onStopJob.)

To track whether or not the app has entered the restricted standby bucket, we recommend logging with the API UsageStatsManager.getAppStandbyBucket() on job execution or UsageStatsManager.queryEventsForSelf() on app startup.

mlock 限制为 64 KB

在 Android 14（API 级别 34）及更高版本中，平台将可使用 mlock() 锁定的最大内存减少为每个进程 64 KB。在以前的版本中，每个进程的大小上限为 64 MB。此限制可促进跨应用和系统更好地管理内存。为了提高各设备之间的一致性，Android 14 针对兼容设备上的新 mlock() 限制添加了新的 CTS 测试。

系统强制使用缓存的应用资源

By design, an app's process is in a cached state when it's moved to the background and no other app process components are running. Such an app process is subject to being killed due to system memory pressure. Any work that Activity instances perform after the onStop() method has been called and returned, while in this state, is unreliable and strongly discouraged.

Android 14 introduces consistency and enforcement to this design. Shortly after an app process enters a cached state, background work is disallowed, until a process component re-enters an active state of the lifecycle.

Apps that use typical framework-supported lifecycle APIs – such as services, JobScheduler, and Jetpack WorkManager – shouldn't be impacted by these changes.

用户体验

关于不可关闭通知用户体验方式的变更

If your app shows non-dismissable foreground notifications to users, Android 14 has changed the behavior to allow users to dismiss such notifications.

This change applies to apps that prevent users from dismissing foreground notifications by setting Notification.FLAG_ONGOING_EVENT through Notification.Builder#setOngoing(true) or NotificationCompat.Builder#setOngoing(true). The behavior of FLAG_ONGOING_EVENT has changed to make such notifications actually dismissable by the user.

These kinds of notifications are still non-dismissable in the following conditions:

  • When the phone is locked
  • If the user selects a Clear all notification action (which helps with accidental dismissals)

Also, this new behavior doesn't apply to notifications in the following use cases:

  • CallStyle notifications
  • Device policy controller (DPC) and supporting packages for enterprise
  • Media notifications
  • The default Search Selector package

数据安全信息更显眼

To enhance user privacy, Android 14 increases the number of places where the system shows the information you have declared in the Play Console form. Currently, users can view this information in the Data safety section on your app's listing in Google Play.

We encourage you to review your app's location data sharing policies and take a moment to make any applicable updates to your app's Google Play Data safety section.

Learn more in the guide about how data safety information is more visible on Android 14.

无障碍功能

非线性字体放大至 200%

Starting in Android 14, the system supports font scaling up to 200%, providing low-vision users with additional accessibility options that align with Web Content Accessibility Guidelines (WCAG).

If you already use scaled pixels (sp) units to define text sizing, then this change probably won't have a high impact on your app. However, you should perform UI testing with the maximum font size enabled (200%) to ensure that your app can accommodate larger font sizes without impacting usability.

安全

最低可安装的目标 API 级别

Starting with Android 14, apps with a targetSdkVersion lower than 23 can't be installed. Requiring apps to meet these minimum target API level requirements improves security and privacy for users.

Malware often targets older API levels in order to bypass security and privacy protections that have been introduced in newer Android versions. For example, some malware apps use a targetSdkVersion of 22 to avoid being subjected to the runtime permission model introduced in 2015 by Android 6.0 Marshmallow (API level 23). This Android 14 change makes it harder for malware to avoid security and privacy improvements. Attempting to install an app targeting a lower API level will result in an installation failure, with the following message appearing in Logcat:

INSTALL_FAILED_DEPRECATED_SDK_VERSION: App package must target at least SDK version 23, but found 7

On devices upgrading to Android 14, any apps with a targetSdkVersion lower than 23 will remain installed.

If you need to test an app targeting an older API level, use the following ADB command:

adb install --bypass-low-target-sdk-block FILENAME.apk

媒体所有者软件包名称可能会隐去

The media store supports queries for the OWNER_PACKAGE_NAME column, which indicates the app that stored a particular media file. Starting in Android 14, this value is redacted unless at least one of the following conditions is true:

  • The app that stored the media file has a package name that is always visible to other apps.

  • The app that queries the media store requests the QUERY_ALL_PACKAGES permission.

Learn more about how Android filters package visibility for privacy purposes.